2 files changed, 42 insertions, 14 deletions

diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 2d5b93000dee..1593a6a632cf 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -397,23 +397,23 @@ static int mmc_select_card(struct mmc_host *host, struct mmc_card *card)
                 return err;
 
         /*
-         * Default bus width is 1 bit.
-         */
-        host->ios.bus_width = MMC_BUS_WIDTH_1;
-
-        /*
-         * We can only change the bus width of the selected
-         * card so therefore we have to put the handling
+         * We can only change the bus width of SD cards when
+         * they are selected so we have to put the handling
          * here.
+         *
+         * The card is in 1 bit mode by default so
+         * we only need to change if it supports the
+         * wider version.
          */
-        if (host->caps & MMC_CAP_4_BIT_DATA) {
+        if (mmc_card_sd(card) &&
+                (card->scr.bus_widths & SD_SCR_BUS_WIDTH_4)) {
+
                 /*
-                 * The card is in 1 bit mode by default so
-                 * we only need to change if it supports the
-                 * wider version.
-                 */
-                if (mmc_card_sd(card) &&
-                        (card->scr.bus_widths & SD_SCR_BUS_WIDTH_4)) {
+                * Default bus width is 1 bit.
+                */
+                host->ios.bus_width = MMC_BUS_WIDTH_1;
+
+                if (host->caps & MMC_CAP_4_BIT_DATA) {
                         struct mmc_command cmd;
                         cmd.opcode = SD_APP_SET_BUS_WIDTH;
                         cmd.arg = SD_BUS_WIDTH_4;
@@ -1055,6 +1055,29 @@ static void mmc_process_ext_csds(struct mmc_host *host)
                 }
 
                 mmc_card_set_highspeed(card);
+
+                /* Check for host support for wide-bus modes. */
+                if (!(host->caps & MMC_CAP_4_BIT_DATA)) {
+                        continue;
+                }
+
+                /* Activate 4-bit support. */
+                cmd.opcode = MMC_SWITCH;
+                cmd.arg = (MMC_SWITCH_MODE_WRITE_BYTE << 24) |
+                          (EXT_CSD_BUS_WIDTH << 16) |
+                          (EXT_CSD_BUS_WIDTH_4 << 8) |
+                          EXT_CSD_CMD_SET_NORMAL;
+                cmd.flags = MMC_RSP_R1B | MMC_CMD_AC;
+
+                err = mmc_wait_for_cmd(host, &cmd, CMD_RETRIES);
+                if (err != MMC_ERR_NONE) {
+                        printk("%s: failed to switch card to "
+                               "mmc v4 4-bit bus mode.\n",
+                               mmc_hostname(card->host));
+                        continue;
+                }
+
+                host->ios.bus_width = MMC_BUS_WIDTH_4;
         }
 
         kfree(ext_csd);
diff --git a/include/linux/mmc/protocol.h b/include/linux/mmc/protocol.h
index 311b6547f561..45c51fd85786 100644
--- a/include/linux/mmc/protocol.h
+++ b/include/linux/mmc/protocol.h
@@ -256,6 +256,7 @@ struct _mmc_csd {
  * EXT_CSD fields
  */
 
+#define EXT_CSD_BUS_WIDTH       183     /* R/W */
 #define EXT_CSD_HS_TIMING       185     /* R/W */
 #define EXT_CSD_CARD_TYPE       196     /* RO */
 
@@ -270,6 +271,10 @@ struct _mmc_csd {
 #define EXT_CSD_CARD_TYPE_26    (1<<0)  /* Card can run at 26MHz */
 #define EXT_CSD_CARD_TYPE_52    (1<<1)  /* Card can run at 52MHz */
 
+#define EXT_CSD_BUS_WIDTH_1     0       /* Card is in 1 bit mode */
+#define EXT_CSD_BUS_WIDTH_4     1       /* Card is in 4 bit mode */
+#define EXT_CSD_BUS_WIDTH_8     2       /* Card is in 8 bit mode */
+
 /*
  * MMC_SWITCH access modes
  */